1. Technical Field
An embodiment of the present invention relates to a vehicle occupant protection system.
2. Description of the Related Art
Japanese Patent Application Laid-open (JP-A) No. H10-250522 discloses a seat structure with a side airbag where a reinforcement cloth that does not easily stretch and is high in strength like the fabric of the airbag is sewn to the reverse surface of a seat back cover. An end edge portion of the reinforcement cloth is sewn to a sewn portion (a splitting portion) of the seat back cover that becomes an inflation position of the airbag. When the airbag deploys, a concentration of stress is produced in the sewn portion by the reinforcement cloth so that the sewn portion quickly ruptures, and thus the seat back cover splits open and the airbag inflates outside the seat back.
Furthermore, JP-A No. 2014-76736 discloses a side airbag device where a webbing is placed around an airbag module. The webbing is attached to a seat back frame together with the airbag module and surrounds the airbag module. Front ends of the webbing are sewn to a splitting portion of a seat cover.
According to the splitting portion using the reinforcement cloth (see JP-A No. H10-250522), early deployability of the airbag at the time of a side crash, for example, can be ensured and at the same time the attachability of the airbag to the side portion of the seat back can be improved compared to the structure where the webbing is placed around the airbag (see JP-A No. 2014-76736). Consequently, in a case where an outside airbag is installed on the vehicle width direction outer side of the seat back and an inside airbag is installed on the vehicle width direction inner side, the splitting portion using the reinforcement cloth can conceivably be disposed in correspondence not only to the outside airbag but also to the inside airbag.
However, the splitting portion using the reinforcement cloth utilizes the tension in the seat back cover to allow the splitting portion to rupture. If, for example, the vehicle width direction inner side splitting portion of the splitting portions on both vehicle width direction sides ruptures first, the tension in the seat back cover drops and it becomes difficult for stress to concentrate in the vehicle width direction outer side splitting portion. If this happens, it is conceivable that it will become difficult for the vehicle width direction outer side splitting portion to rupture.